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I am renting a house and within the past 2 months I have noticed green residue in my toilet, bathroom sink and tub. I have been able to remove the green residue from the bottom of the tub but not the shower walls or the tub. Will someone help me identify the cause of these hard to remove stains and then how to remove them?

Usually when copper is present it has been introduced by the corrosion of copper plumbing. Water containing copper cause blue or green stains on fixtures. Copper also causes green soap curd to form. A water softener removes copper. Raise the pH of the water to at least 8.3. Good luck. Process of elimination.